Locke's theory of classification

In §155 of his New Theory of Vision Berkeley explains that a hypothetical ‘unbodied spirit’ ‘cannot comprehend the manner wherein geometers describe a right line or circle’.1 ¹All references to Berkeley are from, A. A. Luce and T. E. Jessop (eds.), The Works of George Berkeley, Bishop of Cloyne (London: Thomas Nelson and Sons, Ltd., 1948) The following abbreviations are used: An Essay Towards A New Theory of Vision, section x = New Theory x; Philosophical Commentaries, entry x = Commentaries x; Part I of A Treatise concerning the Principles of Knowledge, section x = Principles x. All other references to Berkeley's works are of the form The Works of George Berkeley, Bishop of Cloyne, volume x, page y = Works, x, y. The reason for this, Berkeley continues, is that ‘the rule and compass with their use being things of which it is impossible he should have any notion.’ This reference to geometrical tools has led virtually all commentators to conclude that at least one reason why the unbodied spirit cannot have knowledge of plane geometry is because it cannot manipulate a ruler or a compass. In this article I will show that such an interpretation is flawed. I will instead argue that Berkeley's understanding of Euclidian geometry was based on Isaac Barrow's account of the foundations of geometry. On this view geometrical objects are conceived in terms of the idealized motion that generates the objects of geometry. Consequently, that what the unbodied spirit cannot do in this context is to form an idea of motion rather than being unable to handle geometrical tools.     

Learning to like it: Aesthetic perception of bodies,movements and choreographic structure

Appreciating human movement can be a powerful aesthetic experience. We have used apparent biological motion to investigate the aesthetic effects of three levels of movement representation: body postures, movement transitions and choreographic structure. Symmetrical (ABCDCBA) and asymmetrical (ABCDBCA) sequences of apparent movement were created from static postures, and were presented in an artificial grammar learning paradigm. Additionally, “good” continuation of apparent movements was manipulated by changing the number of movement path reversals within a sequence. In an initial exposure phase, one group of participants saw only symmetrical sequences, while another group saw only asymmetrical sequences. In a subsequent test phase, both groups rated all sequences on an aesthetic evaluation scale. We found that posture, movement, and choreographic structure all influenced aesthetic ratings. Separate ratings for the static body postures presented individually showed that both groups preferred a posture that maximized spatial symmetry. Ratings for the experimental sequences showed that both groups gave higher ratings to symmetrical sequences with “good” continuation and lower ratings to sequences with many path reversals. Further, participants who had been initially familiarized with asymmetrical sequences showed increased liking for asymmetrical sequences, suggesting a structural mere exposure effect. Aesthetic preferences thus depend on body postures, apparent movement continuation and choreographic structure. We propose a hierarchical model of aesthetic perception of human movement with distinct processing levels for body postures, movements and choreographic structure.     

Specificity of Task Constraints and Effects of Visual Demonstrations and Verbal Instructions in Directing Learners' Search During Skill Acquisition

In the present study, the efficacy of visual demonstrations and verbal instructions as instructional constraints on the acquisition of movement coordination was investigated. Fifteen participants performed an aiming task on 100 acquisition and 20 retention trials, under 1 of 3 conditions: a modeling group (MG), a verbally directed group (VDG), and a control group (CG). The MG observed a model intermittently throughout acquisition, whereas the VDG was verbally instructed to use the model's movement pattern. Participants in the CG received neither form of instruction. Kinematic analysis revealed that compared with verbal instructions or no instructions, visual demonstrations significantly improved participants' approximation of the model's coordination pattern. No differences were found in movement outcomes. Coordination data supported the visual perception perspective on observational learning, whereas outcome data suggested that the modeling effect is mainly a function of task constraints, that is, the novelty of a movement pattern.     

Center of Gravity Motions and Ankle Joint Stiffness Control in Upright Undisturbed Stance Modeled Through a Fractional Brownian Motion Framework

The authors modeled the center of gravity vertical projection (CG_V) and the difference, CP - CG_V, which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and t heir spatiotemporal articulation. The results demonstrated that CG_V and CP - CG_V motions are both endowed in complementary tashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CG_V and CG_V than for CP trajectories. Results deduced from both input (CG,) and muscular stiffness (CP - CG_V) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled.     

Changes in Saccadic and Manual Motor Control After Ocular Smooth Pursuit Adaptive Modifications

The gain of ocular smooth pursuit responses can be adaptively modified under certain circumstances. Evidence that these modifications are caused, at least partly, by changes at a sensory level comes from the fact that subsequent manual tracking movements generated during visual fixation are also modified in a similar manner. The question addressed in the present experiment was whether the modifications are constrained specifically to responses such as these, which are driven by retinal image motion, or whether they can also influence movements that make use of retinal image position. This was accomplished by comparing manual and oculomotor responses to step changes in target position before and after smooth pursuit adaptation. The results showed that, as with manual tracking movements, these responses were also modified by the adaptive procedure, although to a lesser extent. In particular, following a 20-min period in which subjects (N = 4) were submitted to a procedure designed to increase the gain of the smooth pursuit system, manual step tracking movements and ocular saccades displayed larger amplitudes than those shown prior to the adaptation. In addition, these gain changes were accompanied by appropriate alterations in response kinematics. Taken together, these results suggest that the mechanisms responsible for adaptive modifications in the smooth pursuit system are also able to more generally influence the processing of visuospatial information. The possible neurophysiological substrate underlying these mechanisms is discussed.     

Perceptual Estimates of Motor Skill Proficiency Are Constrained by the Stability of Coordination Patterns

This study demonstrated that motor skill proficiency ratings are constrained by the same order parameter dynamics that constrain action production and action perception processes. Participants produced rhythmic actions simulated by an animated stick figure of the human arm. The primary finding was that participants’ proficiency ratings covaried most with relative phase (φ) variability compared to mean relative phase. In-phase (φ = 0°) was produced with the least variability and received the highest proficiency rating, whereas the patterns φ = ±150° were attempted with the most variability and received the lowest proficiency ratings. A temporal delay in attempting to produce the animated pattern had a large impact on produced relative phase, yet had little impact on the proficiency ratings. Proprioceptive processes provide individuals information on motor skill proficiency. The lead or lag motion of the hand to forearm segment of the animated arm was identified consistently through visual processes and revealed asymmetries in the mapping of visual input to motor output. The results are consistent with concepts from the dynamic pattern theory of coordination and are discussed with regard to relative phase as an informational variable that constraints the perception-action system across many levels.     

Detection and recognition of emotional expressions: Effects of traits of personality disorder and gender

A problem in the processing of emotions has long been thought to be strongly associated with the aetiology and maintenance of personality disorders. Previous research has demonstrated a hyposensitivity to the faces expressing fear in those high on the traits of psychopathy, while patients with BPD have been shown to be hypersensitive to expressions in general. However, many previous studies could be explained by a bias in reporting particular expressions rather than a change in sensitivity to these expressions. Using two tasks, the present study examined both the detection and the recognition of four emotional expressions (anger, happy, sad, and fear) in a community sample of males and females. Measures of self-reported psychopathy and Borderline Personality traits were administered. The results showed marked gender differences. Psychopathy was negatively related to performance in both the detection and recognition of fear, but only for males. Borderline Personality traits were positively related to overall performance in the recognitions task, but only for females. The results suggest strong differences in the role that emotional processing might play between the genders.     

Digit ratios,but not facial width-to-height ratios,are associated with the priority placed on attending to faces versus bodies

Testosterone has been linked to a sexual preference for bodies rather than faces. Low digit ratio (2D:4D) and high facial width-to-height ratio (WHR) are associated with high prenatal testosterone. We tested whether low 2D:4D and high facial WHR were correlated with a preference for bodies over faces. Our sample consisted of 109 college students (64 males). A two-way analysis of variance demonstrated a significant main effect of digit ratio on the priority placed on paying attention to faces or bodies such that low 2D:4D was linked to a preference for bodies, but the effect of sex was not significant. There were no significant interaction effects. Another two-way analysis of variance revealed no significant effects for facial WHR and attentional priority but significant associations between sex and attentional priority. There were no significant interaction effects. Our findings indicate that individuals with low digit ratios tended to pay more attention to bodies than to faces compared with individuals with higher digit ratios, independently of sex. We also found that males tended to pay more attention to bodies than to faces compared with females, independently of facial WHR.     

Facial expressions can inhibit the activation of gender stereotypes

ABSTRACT

Using faces as the priming stimuli, the present study explored the influence of facial expressions on the activation of gender stereotypes using a lexical decision paradigm. Experiment 1 explored the activation of gender stereotypes when the facial primes contained only gender information. The results showed that gender stereotypes were activated. In Experiment 2, the facial primes contained both gender category and expression information. The results indicated that gender stereotypes were not activated. Experiment 3 required the participants to make emotion, gender, or impression decisions concerning the facial primes before the lexical decision task. The results showed that gender stereotypes were not activated in emotion and impression decisions conditions, whereas stereotypes were activated in gender decisions condition. These finding suggest that facial expressions can inhibit automatic activation of gender stereotypes, unless the perceivers perform gender categorization processing to prime faces intentionally.     

Reduced willingness to approach genuine smilers in social anxiety explained by potential for social evaluation,not misperception of smile authenticity

ABSTRACT

We investigate perception of, and responses to, facial expression authenticity for the first time in social anxiety, testing genuine and polite smiles. Experiment 1 (N?=?141) found perception of smile authenticity was unaffected, but that approach ratings, which are known to be reduced in social anxiety for happy faces, are more strongly reduced for genuine than polite smiles. Moreover, we found an independent contribution of social anxiety to approach ratings, over and above general negative affect (state/trait anxiety, depression), only for genuine smiles, and not for polite ones. We argue this pattern of results can be explained by genuine smilers signalling greater potential for interaction – and thus greater potential for the scrutiny that is feared in social anxiety – than polite smiles. Experiment 2 established that, relative to polite smilers, genuine smilers are indeed perceived as friendlier and likely to want to talk for longer if approached. Critically, the degree to which individual face items were perceived as wanting to interact correlated strongly with the amount that social anxiety reduced willingness to approach in Experiment 1. We conclude it is the potential for social evaluation and scrutiny signalled by happy expressions, rather than their positive valence, that is important in social anxiety.